THE EFFECT OF THYROXINE ON GLAND WEIGHT AND UPTAKE OF RADIOACTIVE PHOSPHORUS BY THE ADRENALS OF THE MOUSE

Abstract
Daily doses of 25 u.g of thyroxine caused marked involution of the thymus, but p32 uptake by the adrenals did not increase until larger doses of thyroxine were used. Thyroxine caused a decrease in the incorporation of p32 into the thymus and a decrease in the total uptake of p32. However, it also caused an increase in the size of the adrenals which in turn caused thymus atrophy. These results suggested that the thyroxine effect on the thymus is a direct one and not mediated through the adrenal.